1. Field of the invention
This invention relates to pick-up arm assemblies for record players.
2. Discussion of the prior art
U.S. Pat. No. 2643 887 describes a pick-up arm assembly for a record player, the assembly comprisng a counterbalance device which includes a counterweight and which is horizontally and vertically pivotally mounted in a pick-up arm mounting, and a pick-up arm comprising a tube having a sound pick-up means disposed at one end thereof. The pick-up arm can only be removed from the pick-up arm mounting in combination with the counterweight. The point of separation on removal, which also forms the horizontal pivotal axis, is a knife edge mounting. If a plurality of sound pick-up systems are to be used one after the other, either they must be respectively mounted on the pick-up arm tube and adjusted, or a plurality of pick-up arms must be provided, each of which is provided with a desired sound pick-up means. For this purpose, however, each pick-up arm must be provided with a precision member, as is required for a knife edge mounting. In addition, the electrical connections must be re-made on each occasion.
In addition, there are known linear pick-up arm arrangements with removable pick-up arm members, in which the balance or the contact force must be re-adjusted on each occasion whenever a change is made in the sound pick-up system or the sound pick-up means.
There are also pick-up arms in which the sound pick-up means is fixed on the pick-up arm. If the sound pick-up means can be removed or replaced at all, this can only be done by means of expensive tools, and requires a considerable amount of time. In addition, a separate sound head can be provided at the front end of the pick-up arm, the sound pick-up means being disposed in the head. This construction affords the possibility of selectively using a plurality of sound pick-up means, by fitting different heads, and in fact it is possible for the sound pick-up means to be changed relatively quickly. However, at each change of the head, the balance for the pick-up arm or the contact force must be re-adjusted. In addition, due to the plug-in connection for the sound head, there is an additional weight at the front end of the pick-up arm tube, and this adds a considerable amount to the moment of inertia of the pick-up arm, which is undesirable since pick-up arms of high quality are required to have the lowest possible moment of inertia.